1. Field of the Invention
The present invention relates to hearing aids. The invention, more specifically relates to a hook for a hearing aid, in particular a BTE-type hearing aid, and a hearing aid utilizing a hook.
2. The Prior Art
BTE-type hearing aids generally have a hearing aid housing comprising a shell in which all of the electronics, including input and output transducers, of the hearing aid are typically located. The shell is worn Behind The Ear, hence the abbreviation BTE. If the output transducer is located in the hearing aid housing, the output sound from the hearing aid is conducted via a sound tube to an earplug placed in an ear of the person wearing the hearing aid.
BTE-hearing aids generally have a hook-shaped part forming the transition from the hearing aid housing in which the sound output transducer is located to the sound tube. This hook-shaped part may be integrally formed with the shell of the hearing aid housing. The hook-shaped part has a curved shape, which may inter alia serve to hold the hearing aid in a correct position behind the ear of the wearer.
Often, however, in BTE-hearing aids the sound tube is not connected directly to the shell of the hearing aid housing. Rather, a separate intermediate piece, commonly referred to as a hook, forms the transition between the shell of the hearing aid housing and the sound tube.
The hook is made from a material which is more rigid than that of the sound tube in order to allow the sound tube to be readily attached thereto and removed therefrom. As the name hook indicates, it has a curved shape. The external shape of the hook is usually so that a smooth transition from the hook to the hearing aid housing, to which it is attached, is obtained. Thus, at the proximal end, where the hook is attached to the hearing aid housing, the external cross-section usually matches that of the hearing aid housing. The hook generally has a taper from the proximal end towards the distal end. Internally the hook has a sound passage extending from the proximal end to the distal end. This passage usually has a circular cross-section, with a constant diameter along the length.
In hearing aids it is well known that feed-back problems exist between the output transducer, and the input transducer. The feed-back is inter alia a problem because it limits the maximum gain achievable with the hearing aid.
The present invention bases itself on the realisation by the inventors that even though the output transducer and input transducer are located in the same housing, the hook attached to the shell of the hearing aid housing, or if the hearing aid has an integral housing, the hook-shaped part extending beyond the output transducer plays a role in these feedback problems.
On this background the present invention sets out to reduce the amount of feed-back between output and input transducers in hearing aids, in particular of the BTE-type. In this respect it should be noted that wherever the present description and claims makes reference to an input transducer, the use of more than one input transducer is not excluded. The skilled person will know that more than one input transducer is commonly used, e.g. in order to obtain directionality, and that the number of input transducers is generally immaterial to the feed-back problems as discussed herein.